Pd/Ga2O3 methanol steam reforming catalysts: Part II. Catalytic selectivity

Lorenz, Harald; Penner, Simon; Jochum, Wilfrid; Rameshan, Christoph; Klötzer, Bernhard

doi:10.1016/j.apcata.2009.02.027

Cited by 52 publications

(108 citation statements)

References 19 publications

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“…They attributed the catalytic activity for methanol synthesis to the reaction of polydentate carbonates with dissociatively adsorbed hydrogen on the Ga 2 O 3 surface, while the addition of Pd only accelerates the reaction by spillover of hydrogen [32]. Penner et al [34] and Lorenz et al [35], however, did observe Pd-Ga alloying and improved selectivity in steam reforming in a study focusing on Pd/ Ga 2 O 3 thin-film model catalysts, but identified different intermetallic compounds than Iwasa's group.…”

Section: Introductionmentioning

confidence: 99%

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Haghöfer

Föttinger

Girgsdies

et al. 2012

Journal of Catalysis

106

138

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Pd/Ga2O3 methanol steam reforming (MSR) catalysts were characterized in detail by utilizing a range of in situ techniques of varying surface sensitivity. Correlating the nature of the intermetallic Pd-Ga compound (IMC; formed upon reduction) with the corresponding activity/selectivity revealed pronounced differences. Generally, a dynamic response of the catalyst surface to the surrounding gas environment was observed. Special attention was paid to the bulk and surface stability of the Pd-Ga IMCs. Whereas the bulk was stable in O2, decomposition of the surface occurred resulting in a partial coverage by GaxOy islands. In addition, we focused on the formation mechanism of undesired CO and were able to identify the reasons limiting the selectivity to MSR. We observed a detrimental effect of CO on the selective Pd-Ga intermetallic compound, causing partial decomposition of the IMC to metallic Pd at the surface. Consequently, patches of Pd metal are present under reaction conditions, catalyzing the unwanted parallel methanol decomposition reaction.

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Section: Introductionmentioning

confidence: 99%

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Haghöfer

Föttinger

Girgsdies

et al. 2012

Journal of Catalysis

106

138

View full text Add to dashboard Cite

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“…This strategy, which involves the preparation of the Pd-In particles by reduction in hydrogen, has proven its capabilities in studies on the corresponding Pd-Ga system [7,8]. On the one hand the thin film model approach allows to prepare and characterize well-defined Pd-In bimetallic particles, grown on single-crystalline NaCl(001) surfaces, with respect to morphology, composition and catalytic selectivity.…”

Section: Introductionmentioning

confidence: 99%

Pd–In2O3 interaction due to reduction in hydrogen: Consequences for methanol steam reforming

Lorenz

Turner

Lebedev

et al. 2010

Applied Catalysis A: General

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104

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Two different Pd/In2O3 samples including a thin film model catalyst with well-defined Pd particles grown on NaCl(001) supports and a powder catalyst prepared by an impregnation technique are examined by Electron Microscopy, X-ray Diffraction and catalytic measurements in methanol steam reforming in order to correlate the formation of different oxide-supported bimetallic Pd-In phases with catalytic activity and selectivity. A PdIn shell around the Pd particles is observed on the thin film catalyst after embedding the Pd particles in In2O3 at 300 K, likely because alloying to PdIn and oxidation to In2O3 are competing processes. Increased PdIn bimetallic formation is observed up to 573 K reduction temperature until at 623 K the film stability limit in hydrogen is reached. Oxidative treatments at 573 K lead to decomposition of PdIn and to the formation of an In2O3 shell covering the Pd particles, which irreversibly changes the activity and selectivity pattern to clean In2O3. PdIn and Pd2In3 phases are obtained on the powder catalyst after reduction at 573 K and 673 K, respectively. Only CO2-selective methanol steam reforming is observed in the reduction temperature range between 473 K and 573 K. After reduction at 673 K encapsulation of the bimetallic particles by crystalline In2O3 suppresses CO2 formation and only activity and selectivity of clean In2O3 are measured.

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“…The same applies to unsupported Pd-rich Pd 2 Ga samples 25 . In contrast, a supported Pd 2 Ga intermetallic compound on Ga 2 O 3 catalyst is highly active and selective as has been shown by Lorenz et al 22,26 . By comparison of the PdGa near surface intermetallic phase with Ga 2 O 3 -supported PdGa compounds, as e.g.…”

Section: Application Of the Uhv-setup And High Pressure Reaction Cellmentioning

confidence: 88%

“…By comparison of the PdGa near surface intermetallic phase with Ga 2 O 3 -supported PdGa compounds, as e.g. studied by Lorenz et al 22 , the importance of the (bi-)metal-oxide contact area could be directly demonstrated. temperature range of 543 K -573 K, the CO 2 -selective MSR reaction is prevalent, but above 573 K, the selectivity changes towards CO because the catalyst undergoes structural changes.…”

Section: Application Of the Uhv-setup And High Pressure Reaction Cellmentioning

confidence: 97%

See 1 more Smart Citation

Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

Mayr

Rameshan

Klötzer

et al. 2014

Review of Scientific Instruments

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An ultra-high vacuum (UHV) setup for "real" and "inverse" model catalyst preparation, depth-resolved near-surface spectroscopic characterization and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the allquartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in-situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy (AES) and low-energy ion scattering (LEIS) measurements. Due the dedicated geometry of the X-ray gun (54.7°, "magic angle") and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depth, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained.To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming (MSR) on PdGa and PdZn near-surface intermetallic phases (NSIP) are shown.3

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Pd/Ga2O3 methanol steam reforming catalysts: Part II. Catalytic selectivity

Cited by 52 publications

References 19 publications

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Pd–In2O3 interaction due to reduction in hydrogen: Consequences for methanol steam reforming

Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

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